Smelting furnace for black liquor



2 Sheets-Sheet 1 www A. G. KERNIN SMEL'TING FURNAGE FOR BLACK LIQUOR Filed Jan. 9, 1952 June 11, 1935.

June 11, 1935. A, Q KERNlN y 2,004,205 v SMELTING FURNACE FOR BLACK LIQUOR` Filed Jan. 9, 1932 2 Sheets-Sheet 2 i W HQE@ C g N Patented June 11, 1935 l, UNITED STATES 2,004,205 sMEL'rING FURNACE Fon BLACK LIQUoa Alfred G. Kernin, Mosnee, SWiS., assignor` to Mosinee Paper Mills Company, Mosmee, Wis., a corporation of Wisconsin Application Janpory 9, 193,2, serial No. 585,656

2 claims. (c1. 23-277) l This invention relates to an apparatusV for the recovery of chemicals in the sulfate process for the manufacture of pulp. I

In the manufacture of sulfate'pulp, a closed 5 tank or digester ispartly iilled with chipsof wood `andV a liquor, the active components of which are largely sodium hydroxide and sodium sulphide. Steam underpressure is introducedinto -the digester and the charge is cooked. The dispent cooking liquor is drained off and the fiber washed. This spentliquor, known' as black liquor, lcontains practically all of the chemicals in changed form that were used for the cooking and, inaddition, the organic substances removed `from the wood.V Before the chemicals in the liquor can' evaporators where it `is concentrated. The highly concentrated resulting mixture is, according to general practice, burned in a rotary furnace, or i incinerator, to form a clinker known as`black ash. Black ash is mixed with sodium sulfate and reduced in a smelting furnace and the resulting -mixture produced therein is drained into a dis-` solving Vtank. The solution thus formed is drawn into another tank where lime is added to causticize the sodium carbonate present and the liquoril allowed to settle. The clear solution from this tank is drawn off and used again for charging the digester. Y o

It is an object of this invention to provide a combined black liquor combusting `andsmelting furnace for use in 'a process as herein described, which will perform the function of the rotary furnace and the reducing furnace.V

It is a further object of this invention to produce a furnace in which the burning of the black Aand a bottom wall '3. gester istthen emptied into diffusers where the I uor, vthat is, the reclamation of the chemicals, the liquor is ordinarily passed through arv series' ofl Figure2 is atransverse sectional view ofthe furnace and tank shown in Figure l.

,o As shown-on the drawings:

My improved furnace A is supported above the dissolving tank B and has mounted therein a boiler C which is connected'by a suitable ilue to a disc evaporator D.

The tank B comprises end walls I, side walls 2, The end walls and side walls extend below the bottom wall to form supports 4 and `5, respectively, "to support the tank. The top wall 6 substantially covers the tank and is supported by the sides and end walls and a number of posts iI located in the tank. I I

Supports 8 extend up from the bottomV ofthe tank and a platform 9 isformed across the top of said supports. The platform 9 and the top wall 6 of the tank formlthe main support for the furnace. The platform 9 is located below the top `wall ofthe tank and the part of the furnace sup- I ported thereby extends through anopening in the topl wall as will be hereinafter described.

Side walls I0 and Il, a rear wall I3, and a front wall I2 together with the bottom walls `I5 and-I6 form the` rire box of the furnace. The frontwall I2 extends a substantial distance below the` end of the rear wall Ii.` An intermediate wall I 4 `extending from substantially the bottom level of the front wall to the bottom level of the rear wall is located parallel `to the end walls and close to the` front wall to form a pit I4a adjacent 'the front` wall. The pit IIIa extends thru the opening in the tank and is supportedon platform 9. `'I'he bottom wall of the furnace is formed in two sections, one sectionl I5 extending rearwardlyv yandv upwardlyl from theV intermediate Wall I4 `to the` rear wall-| 3 and forms with the side walls I0 and Hand therear wall I 3, the combustion I zone of the furnace.V The section I6 of the bottom'wall of the furnace extends forwardly and .downwardly from the end of the intermediate wallbelow and beyond the front wall. Section I6 .slopes` from the sides to the middle line,` thereby forming a V-shaped trough II and leaving an opening I1a between the front wall and the bottom fora purpose hereinafter described.

Earth filler I9 is provided on the top wall li ofY the tank to support the bottom and side walls of the furnace. The earth filler may extend to the ends of the furnace or a platform such as shown at I8 may be used to support the end wall of the furnace. Likewise, earth filler I9 on platform 9 is used to support the front section I6 of the furnace bottom.

'I'he side wall II is provided with a manhole 20 Y the evaporation of other black liquor. 'VA platform 3| Yis supported by posts 3201i the top wall cof the introduction of the black liquor. Vis connected to and opens into the pipe 23 Vto supply the furnace with air. The pipe 2,5 is used also for the introduction of the sodium sulfate. In practice it has been found vadvantageous to locate the pipe 23 about midway ofthe end walls and slightly above the inclined section l5, and also to direct the open endfof the pipe towards the rear wall as shown at 2B. 1

Tuyeres 21 are located in the forward and lower end of the side walls and are given a downward slant so as to direct a current of air toward the bottom of the pit Ma. The amount of air introduced into the pit is regulated by valvesl 21a located on the ends of tuyeres 2l.

The' boiler C is supported within the furnace as shown and may be of anyY standard construction and provided, if desired, with a super heater 28.V A pipe line 29 supplies the boiler with Vwater or other liquids to be heated. The boiler is used for the purpose of utilizing theheat `ofthe furnace and forms no part of my invention. -The hot gases from the furnace are drawn through the boiler and through a v`rpipe line't toa disc evaporator shown at D where the hot gases assist in the tank. rIfhe platform enables Vthe operator'to drawnfrom this tank into another tank'(not have access to the boiler for thepurpose fof cleaningit. Y, Y The wallsiof the tank and the supports located Vtherein are preferably formed of reinforced con cretefand the'walls of the furnace are preferably made of fire brick.

In operation, the highly' concentrated black liquor from the evaporator is supplied to the furnace through the' pipes 24 and 23. vAir and s0- Vdium sulfate are introduced Ythrough the pipe 25 Y matter. A carefully regulated amount of oxygen is introduced into the lpitthrough the :tuyeres 21 and the burning continues, the .carbon .uniting with the air and also with the oxygen of thecontained chemicals to cause a reduction ofthe sulfates. Smelted chemicals' pass out through the' opening lia between theffront lwall and the bot-- tom of the furnace and into .the dissolving tank B. TheV` solution of the dissolved chemicals is shown) in which the nsolution is mixed with lime r in one operation.

and allowed to settle. is drawn oif and again used in the digesting of the pulp.

Heretofore, in regenerating the black liquor, the syrupy black liquor from the evaporators, has been drawn to a rotary incinerator where the evaporation was completed and the resulting black ash was taken therefrom andA reducedfin a smelting furnace. By using my improved furnace, it is now possible to accomplish these two steps My improved furnace is adapted to receive the black liquor from the evaporators and to complete the evaporation thereof, and also to reduce the chemicals contained in partially burned residues formed in the upper part of the furnace. -It will be readily seen that by the use of my improved furnace, the time and the expense Iam aware that many changes maybe made and numerous details of construction may be varied-:through a wide range withoutv departing from theprinciples of VthisV invention, and I, therefore,A 'do not purpose limiting the patent granted hereon otherwise vthan is necesstatedby the prior art.

i claim'as my invention: 1

l. A furnacevfor the evaporation and reduction of blackV liquor comprising two side walls, a front wall and a rear wall, the front Wall .extending'below the rear wall, an intermediate wall parallel to and adjacent the fron-t wall, and inclined bottom wall extending rearwardly and upwardly Vf-rom the intermediate wall to the rear wall and forming, with the side and rear walls, the -corn-V hustion zone jof the furnace, a V-.shaped `bottom wall extending downwardly and forwardlyffrom the Vintermediate wall below the front wall and forming with the Ifront wall and side wall a reduction pit, said iront wall having an'opening fat the bottom of said pit, a pipe having connections for receiving black liquor and air extending through the side wall and terminating ashort distanceV inside thereof and at such location that` the contents thereof are discharged over the upper inclined section ofthe bottom wall, and ducts passing through the lower, forward endof the side wall for introducing a regulatedamount vof air to the lower ,section of the Afire box. l

2. A furnace for theregeneration of black liquor having a two-part bottom, each part being iloupper combustion zone and a lower reduction zone, the bottom .ofv the upper zone extending upwardly and rearwardly from .the reduction zone, ,atuyere forV introducing a mixture .of Vblack liquor and air to the combustion zone, vsaid tuyere extending to the rear -of Asaid combustion zone to .direct said stream awayfromjs'aid reduction zone and ducts for 4introducing airV to the lower'combustion zone. Y

ALFRED G.

From thence, the liquory Ycated vatV a different level to thereby provide `an i 

